Method of making well-points for de-watering ground

ABSTRACT

A disposable wellpoint for dewatering ground comprises a body of spirally-corrugated perforated tubing formed of plastics material and covered by a filter sleeve of nylon fabric, and a suction pipe of spirally corrugated tubing enters the top end of the body. The body, the sleeve, and the suction pipe can be severed as lengths from supply reels on site, and the assembled wellpoints can be introduced into the ground in a tubular casing provided with water lances.

United States Patent [191 Allen et al.

[ 1 Dec. 18, 1973 METHOD OF MAKING WELL-POINTS FOR DE-WATERING GROUND [75] Inventors: Ronald Noel Allen; Ernest William Potter, both of London, England [73] Assignee: Henry Sykes Limited, Charlton,

London, England [22] Filed: Jan. 3, 1973 [21] Appl. No.: 320,805

Related U.S. Application Data [62] Division of Ser. No. 144,836, May 19, 1971.

[30] Foreign Application Priority Data June 1, 1970 Great Britain ..26388/70 [52] U.S. Cl. 29/l63.5 F, 29/412, 29/428 [51] Int. Cl B23p 15/16 [58] Field of Search 29/1635 F, 428,

[56] References Cited UNITED STATES PATENTS 5/1896 Smith 166/230 1,218,848 3/1917 Foster 210/110X 1,229,437 6/1917 Foster 210/458 1,367,406 2/1921 McLean 29/1635 CW 2,046,456 7/1936 Johnson 29/1635 CW X 2,969,840 1/1961 DAudiffret et a1. 166/227 X 3,221,819 12/1965 Dickinson et a1 166/233 3,638,726 2/1972 Sibley 166/236 Primary Examiner-Charles W. Lanham Assistant Examiner-V. A. DiPalma Attorney-Hall, Pollock & Vande Sande 5 7 ABSTRACT A disposable wellpoint for dewatering ground comprises a body of spirally-corrugated perforated tubing formed of plastics material and covered by a filter sleeve of nylon fabric, and a suction pipe of spirally corrugated tubing enters the top end of the body. The body, the sleeve, and the suction pipe can be severed as lengths from supply reels on site, and the assembled wellpoints can be introduced into the ground in a tubular casing provided with water lances.

4 Claims, 2 Drawing Figures METHOD OF MAKING WELL-POINTS FOR DE-WATERING GROUND BACKGROUND OF THE INVENTION This invention relates to wellpoints for dewatering ground.

Wellpoints are, of course, well known and most wellpoints are of the general kind described in our British Pat. No. 1,012,282. This known type of wellpoint is relatively expensive, as it must be robustly constructed of corrosion-resistant materials, and difficulty is frequently encountered in withdrawing the wellpoints from the ground after an operating period which may extend over several months or more. Also, the wellpoints, and particularly the filters, must usually be reconditioned before being used again.

Furthermore, conventional wellpoints are heavy to handle and store, and the difficulties involved in storage are further increased where a variety of sizes and types of wellpoint must be stocked to meet the varying site conditions which usually exist to a greater or lesser extent.

It is an object of the present invention to overcome or at least reduce the above disadvantages.

SUMMARY OF THE INVENTION According to the present invention there is provided a wellpoint comprising a tubular body of shapesustaining plastics material provided with a lower end closure and an upper end part arranged to receive a suction pipe, said body being formed with a series of filter openings, and a sleeve of synthetic fabric or the like surrounding the tubular body to filter water being drawn into the tubular body through said filter opening.

Preferably, said tubular body has a diameter greater than said suction pipe and said upper end part comprises an end cap having a central opening to receive said pipe.

The invention also provides a tubular body as defined above for use in a wellpoint.

Further according to the invention, there is provided a method of producing a wellpoint for dewatering ground, comprising taking from a supply a length of shape-sustaining plastics tubing formed with a series of filter openings, taking from a supply a length of imperforate shape-sustaining plastics tubing of a diameter substantially smaller than that of the perforated tubing, inserting an end length of the imperforate tubing into the upper end of the perforated tubing, effectively clos-- ing the still-open ends of the perforated tubing and securing a sleeve of synthetic fabric around the perforated tubing.

According to a further feature of the invention, there is provided a method of dewatering ground comprising introducing a wellpoint as defined above into the ground by means of a hollow tubular casing in which the wellpoint is accommodated, the method including the step of easing the entry of the tubular casing into the ground by means of one or more water lances attached to or integral with the casing, the casing being extracted when the wellpoint has reached its required operating depth.

Other objects and features of the invention will appear from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a partly sectional elevation showing a wellpoint according to the invention: and,

FIG. 2 is a diagrammatic sectional elevation showing the wellpoint illustrated in FIG. 1 accommodated in a placement casing provided with water pressure lances.

DESCRIPTION OF THE PREFERED EMBODIMENTS Referring to FIG. 1. of the drawings, the wellpoint comprises a tubular body 10 consisting of a length of hard plastics tubing, for example P.V.C. The tubing is formed with a spiral corrugation 11, and series of perforations 12 are formed in the trough of the corrugation to provide coarse filter openings. An unperforated, lower end blanking cap 13 closes one end of the body 10 and.an upper end cap 14 formed with a central opening is arranged at the upper end of the body 10. The end caps are also formed with spiral corrugations, and can thus be screwed onto, or in a modification into, the body 10. A pipe 15 of similar plastics material, having an angled bottom end 15A, extends through the upper end cap 14 to penetrate into and, as shown, along the complete length of the body 10. The pipe 15 is also formed with a strengthening spiral corrugation and may be partly screwed into the opening in cap 14.

A sleeve of nylon fabric 16 encloses the body 10, the sleeve being knotted at 17 and being held closely around the pipe 15 where the latter enters cap 14, by means of a rubber ring 18.

In use, the wellpoint shown in FIG. 1 is introduced into a tubular casing 19 shown in FIG. 2, and it will be noted that water pressure lances 20 are secured to the casing 19. As shown, the casing 19 comprises a lower length of metal tube into which an upper length of smaller-diameter tube is force-fitted or welded. The wellpoint is introduced into the ground by the scouring action of the water from the lances 20, which eases the passage of the casing 19 through the ground to be dewatered. A certain amount of sand or soil may pass upwardly through the bore of the casing 19 and tend to stop the downward progress of the wellpoint, but such sand and soil are mixed with water to form a slurry and the resistance is not great; furthermore, the wellpoint is sufficiently rigid to be pushed down by pressure from ground level and, indeed, a metal or like rod may be passed through the tube 15 gently to engage the bottom end cap 13 and so assist downward movement of the wellpoint.

On the wellpoint reaching its required operating depth, the outer casing together with the lances 20 are withdrawn, and the pipe 15 is connected to a header pipe (not shown) which is in turn connected to a suction pump such as that marketed under our Trade Mark VELOVAC or UNIVAC. It will be appreciated that suction through the pipe 15 will cause water from the surrounding ground to be drawn through the nylon sleeve 16 and the perforations 12 into the body 10 and this water, which has been filtered by the nylon sleeve, will be drawn upwardly through pipe 15. It will also be appreciated that, since there is a reduced pressure within the body 10, it is not necessary to have hermetically sealed end caps 13 and 14 and, likewise, the suction will draw the nylon sleeve into close engagement with the pipe 15 where the pipe enters the end cap.

It has been found that, due probably to the corrugation in the body 10, the nylon sleeve tends to vibrate and this produces a self-cleansing action in the nylon sieeve. Also, the corrugation promotes swirling of the indrawn water to effect clearing of the perforations 12.

After the dewatering operation has been completed, which may of course take several months, the pipe 15 is withdrawn. The body may also be withdrawn but, since these bodies are relatively inexpensive, they will generally be regarded as disposable and will be left in position in the ground; indeed, more or less of the pipe 15, which is also inexpensive, may also be left in the ground if its extraction proves difficult.

The drawbacks and disadvantages of conventional wellpoints can thus be at least partly reduced by the arrangement described above. For example, the wellpoints can be produced on site from reels of corrugated tubing which forms the body 10, reels of corrugated or plain tubing which forms the pipe 15, and reels of nylon sleeve which forms the sleeve 16. It has been found satisfactory to employ a body 10 having a diameter of approximately 3 inches, and most known requirements can be met by varying the length and/or the diameter of the body 10; also, the degree of filtration can be chosen by selecting an appropriate mesh for the nylon sleeve 16. Furthermore, the materials employed in the wellpoint according to the present invention are lightweight and are corrosion and damp resistant for long periods of time in the ground and in storage.

Modifications may be made, without departing from the scope of the invention. For example, the lower end of the (open) nylon sleeve may be tucked into the tubular body 10 and the end cap 13 then applied to hold the sleeve and render the knot 17 unnecessary; the upper end of the sleeve may likewise be tucked in and held by the cap 14. The end cap 13, possibly together with the cap 14, may also be formed with perforations (if fabriccovered). Furthermore, the end caps 13 and 14 may be formed of similar shape, the upper end cap then being cut, possibly on site, to receive the pipe 15.

The invention has so far been described in relationship to the dewatering of ground, but the same wellpoint and process may be employed for other purposes, such as providing a more or less temporary stand pipe for water-supply.

We claim:

1. A method of producing a wellpoint for dewatering ground, comprising taking from a supply a length of shape-sustaining plastics tubing formed with a series of filter openings, taking from a supply a length of imperforate shape-sustaining plastics tubing of a diameter substantially smaller than that of the perforated tubing, inserting an end length of the imperforated tubing into the upper end of the perforated tubing, effectively closing the still-open ends of the perforated tubing and securing a sleeve of synthetic fabric around the perforated tubing.

2. A method according to claim 1, in which said perforated tubing is severed as a length from a supply reel on site.

3. A method according to claim I, in which said imperforate tubing is severed as a length from a supply reel on site.

4. A method according to claim 1, in which said sleeve of synthetic fabric is severed as a length from a supply reel on site. 

1. A method of producing a wellpoint for dewatering ground, comprising taking from a supply a length of shape-sustaining plastics tubing formed with a series of filter openings, taking from a supply a length of imperforate shape-sustaining plastics tubing of a diameter substantially smaller than that of the perforated tubing, inserting an end length of the imperforated tubing into the upper end of the perforated tubing, effectively closing the still-open ends of the perforated tubing and securing a sleeve of synthetic fabric around the perforated tubing.
 2. A method according to claim 1, in which said perforated tubing is severed as a length from a supply reel on site.
 3. A method according to claim 1, in which said imperforate tubing is severed as a length from a supply reel on site.
 4. A method according to claim 1, in which said sleeve of synthetic fabric is severed as a length from a supply reel on site. 